mbedtls_freertos_port.c

/*
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

/**
 * @file mbedtls_freertos_port.c
 * @brief Implements mbed TLS platform functions for FreeRTOS.
 */

#include <stdlib.h>
#include <string.h>

/* FreeRTOS includes. */
#include "FreeRTOS.h"
#include "semphr.h"

/* mbed TLS includes. */
#if defined( MBEDTLS_CONFIG_FILE )
    #include MBEDTLS_CONFIG_FILE
#else
    #include "mbedtls/mbedtls_config.h"
#endif
#include "mbedtls/entropy.h"

#include "mbedtls_freertos_port.h"

/*-----------------------------------------------------------*/

/**
 * @brief Allocates memory for an array of members.
 *
 * @param[in] nmemb Number of members that need to be allocated.
 * @param[in] size Size of each member.
 *
 * @return Pointer to the beginning of newly allocated memory.
 */
void * mbedtls_platform_calloc( size_t nmemb,
                                size_t size )
{
    size_t totalSize = nmemb * size;
    void * pBuffer = NULL;

    /* Check that neither nmemb nor size were 0. */
    if( totalSize > 0 )
    {
        /* Overflow check. */
        if( ( totalSize / size ) == nmemb )
        {
            pBuffer = pvPortMalloc( totalSize );

            if( pBuffer != NULL )
            {
                explicit_bzero( pBuffer, totalSize );
            }
        }
    }

    return pBuffer;
}

/*-----------------------------------------------------------*/

/**
 * @brief Frees the space previously allocated by calloc.
 *
 * @param[in] ptr Pointer to the memory to be freed.
 */
void mbedtls_platform_free( void * ptr )
{
    size_t xBlockLen = malloc_usable_size( ptr );

    if( xBlockLen > 0 )
    {
        explicit_bzero( ptr, xBlockLen );
        vPortFree( ptr );
    }
}

/*-----------------------------------------------------------*/

#if defined( MBEDTLS_THREADING_C )

/**
 * @brief Creates a mutex.
 *
 * @param[in, out] pMutex mbedtls mutex handle.
 */
    static void mbedtls_platform_mutex_init( mbedtls_threading_mutex_t * pMutex )
    {
        configASSERT( pMutex != NULL );

        /* Create a statically-allocated FreeRTOS mutex. This should never fail as
         * storage is provided. */
        pMutex->mutexHandle = xSemaphoreCreateMutexStatic( &( pMutex->mutexStorage ) );
        configASSERT( pMutex->mutexHandle != NULL );
    }

/*-----------------------------------------------------------*/

/**
 * @brief Frees a mutex.
 *
 * @param[in] pMutex mbedtls mutex handle.
 *
 * @note This function is an empty stub as nothing needs to be done to free
 * a statically allocated FreeRTOS mutex.
 */
    static void mbedtls_platform_mutex_free( mbedtls_threading_mutex_t * pMutex )
    {
        /* Nothing needs to be done to free a statically-allocated FreeRTOS mutex. */
        vSemaphoreDelete( pMutex->mutexHandle );
    }

/*-----------------------------------------------------------*/

/**
 * @brief Function to lock a mutex.
 *
 * @param[in] pMutex mbedtls mutex handle.
 *
 * @return 0 (success) is always returned as any other failure is asserted.
 */
    static int mbedtls_platform_mutex_lock( mbedtls_threading_mutex_t * pMutex )
    {
        BaseType_t mutexStatus = 0;

        configASSERT( pMutex != NULL );

        /* mutexStatus is not used if asserts are disabled. */
        ( void ) mutexStatus;

        /* This function should never fail if the mutex is initialized. */
        mutexStatus = xSemaphoreTake( pMutex->mutexHandle, portMAX_DELAY );
        configASSERT( mutexStatus == pdTRUE );

        return 0;
    }

/*-----------------------------------------------------------*/

/**
 * @brief Function to unlock a mutex.
 *
 * @param[in] pMutex mbedtls mutex handle.
 *
 * @return 0 is always returned as any other failure is asserted.
 */
    static int mbedtls_platform_mutex_unlock( mbedtls_threading_mutex_t * pMutex )
    {
        BaseType_t mutexStatus = 0;

        configASSERT( pMutex != NULL );
        configASSERT( pMutex->mutexHandle != NULL );
        /* mutexStatus is not used if asserts are disabled. */
        ( void ) mutexStatus;

        /* This function should never fail if the mutex is initialized. */
        mutexStatus = xSemaphoreGive( pMutex->mutexHandle );
        configASSERT( mutexStatus == pdTRUE );

        return 0;
    }

/*-----------------------------------------------------------*/

    #if defined( MBEDTLS_THREADING_ALT )
        int mbedtls_platform_threading_init( void )
        {
            mbedtls_threading_set_alt( mbedtls_platform_mutex_init,
                                       mbedtls_platform_mutex_free,
                                       mbedtls_platform_mutex_lock,
                                       mbedtls_platform_mutex_unlock );
        }

    #else /* !MBEDTLS_THREADING_ALT */

        void (* mbedtls_mutex_init)( mbedtls_threading_mutex_t * ) = mbedtls_platform_mutex_init;
        void (* mbedtls_mutex_free)( mbedtls_threading_mutex_t * ) = mbedtls_platform_mutex_free;
        int (* mbedtls_mutex_lock)( mbedtls_threading_mutex_t * ) = mbedtls_platform_mutex_lock;
        int (* mbedtls_mutex_unlock)( mbedtls_threading_mutex_t * ) = mbedtls_platform_mutex_unlock;

    #endif /* !MBEDTLS_THREADING_ALT */

#endif /* MBEDTLS_THREADING_C */
/*-----------------------------------------------------------*/